A former Turkish military chief on trial for allegedly plotting to overthrow the government walked out of court on Tuesday, saying the charges against him are frivolous.

Former army chief Ilker Basbug stormed out of the hearing after prosecutors played tapes of phone conversations between two other suspects in the alleged plot against Prime Minister Recep Tayyip Erdogan's government. Basbug angrily protested against the use of the tapes.

Earlier, he denied involvement in the alleged terrorism plot, known as Ergenekon, and refused to defend himself or recognize the court's authority.

Basbug later returned to the courtroom inside the Silivri prison complex, near Istanbul, where he has been held since January. He refused to answer questions. Reuters news agency says the court later adjourned his trial until Thursday.

Basbug is the most senior official arrested in connection with Ergenekon, a secularist network the government says was planning bombings and other attacks to discredit Turkey's Islamic-based government and trigger a military coup.

The former general went on trial on Monday on charges of playing a leading role in the alleged network. Prosecutors also say Basbug used an Internet campaign to try to destabilize the government.

Turkish authorities have detained more than 300 people, including journalists, academics and politicians as part of a wide-reaching investigation into Ergenekon.

In January, the U.S. urged Turkey to handle any prosecution of Basbug and the other suspects with transparency and to respect due process.